Heres a New One???

[Deep C]

Things that make you say hmmmmm?

Last week took the 31 for a spin. Had some issues with the fuel lifting pump on port motor and found a little water in the fuel. Switched off main tank which was low to the saddles.... Should be nothing special. Done that before plenty of times.

Got aboard this morn and lit em up. Looked at the guages and something immediately caught my eye. My starboard saddle tank was reading near empty when it should be nearly full. The port was where it should be. But the main now showed much fuller than last week?

I tapped on the glass and sticked the tanks and found the guages to be spot on... So I can see what has happened... Somehow the starboard saddle tank has siphoned back into the main tank. What I don't get is how the h*** did that happen?

The tanks in this contender are under the deck and surrounded by glass so I can't see how they sit> I'm gonna have to assume that the saddles are higher or perhaps on top of the main. That could explain some of the gravity physics at play. What I don't get is how the fuel would be drawn up hill from the one tank to where it valves at the filter? Then how would it get back through the other closed valve to flow backards into the main? I are confused...

[rbrdogs]

Are you absolutey sure of yesterday's levels in both tanks? It could be a case od ARADD (age related attention deficit disorder). It just doesn't seem possable to me, but I don't know the set up.

Bert

[Deep C]

Yes Bert... I'm sure... Might have a touch of grey in the ol moustache but no cobwebs in the dome ... yet... All I can think of is that perhaps the saddles sit on top of the Main (On the sides) and that the valve wasn't all the way closed... Might try "cracking" the other sides valve and see if it happens there too...

[clt_capt]

if it can siphon, it would seem like a poor design... Did you have more weight in the bow than normal? Is is possible that you didn't get the main valve completely shut - That could possibly allow the siphon to start...

[Deep C]

She sits level on a rack... Yes its possible main valve want shut completely...
Never had it happen before but lots of things I havn't had the pleasire of "learning" about yet...

[seapower]

Don't worry Deep, it's just making fuel. Draw the system with all the plumbing and valves on a piece of paper. Most of the time, if you can "see" it, you can figure it out. Of course at your age, "seeing" it may be a problem. In that case use crayons, really bright colors help too. Frank

[Deep C]

Haayyyy I'm way too young to be old...
I have hunches but would have thought there would be something in all that hardware to prevent back flow. Without tearing the thing apart I'm gonna have to assume that the saddles ride on top and on the sides of the main and that the hoses must be run straight instead of up and around stuff.
Not the end of the world but I like my saddles for back up and the idea of them siphoning down to the main when I'm not looking bugs me... I'd hate on a long run to run out the main then switch only to find that one or both saddles is empty... I don't have the option of running both engines off one saddle (they each have their own) (But they share the main) ...

[Lure-Head]

I’ve heard of this only one time in the past. It was and, still is, strongly believed that osmosis was the culprit. Hope this helps !!!

[Deep C]

Osmosis.... Hmmm... Monel as a permeable membrane... Whoda thunk it...?
Right now I guess its one of those "things" I gotta keep an eye on... Guess the best thing I can do is just keep all three tanks full. Should do that to keep condensation moisture down any way. That gets tricky down here in the sun and heat. Can't fill to the top cause it will expand and run out the vents so guess where "safe full" is. Then check to see that the one valve does close all the way. Still gotta run the saddles down now and then to avoid gas getting old...